> > Web browsers don't "pick a random sleep time before trying again", though; > they display a 500 error page and the user promptly clicks "reload" while > making an exasperated sigh. >
That sounds like "picking a random sleep time before trying again" to me :-) > If the client is something other than a web browser, then we're no longer > talking about the web, but some other thing, like SMTP or whatever. And > then we're outside the scope of my earlier remark, which specifically > mentioned the web. Not to mention outside the scope of the OP's product, > which was clearly referred to as a "Ring middleware" and not some other > sort of server component for some other kind of server. > > Or were you meaning to suggest that the *users* pick a random sleep time > before trying again? Good luck herding them cats. See also > http://en.wikipedia.org/wiki/Wicked_problem ... > > > > On Sat, Nov 16, 2013 at 4:24 PM, James Reeves <ja...@booleanknot.com>wrote: > >> It may be useful for certain web services. If the server gets overloaded >> by a temporary spike, the clients could pick a random sleep time before >> trying again. >> >> - James >> >> >> On 16 November 2013 21:15, Cedric Greevey <cgree...@gmail.com> wrote: >> >>> I can think of very few web apps where this would be a desirable >>> approach. A user getting a spurious error in response to a URL that they >>> *know* is valid is just going to hammer on the "reload" button until they >>> get a correct response from the server. So the server will end up even more >>> congested than if it just responded sluggishly but otherwise normally to >>> the request. >>> >>> >>> On Sat, Nov 16, 2013 at 1:21 PM, Rob Day <r...@rkd.me.uk> wrote: >>> >>>> Hi all, >>>> >>>> I've just published the first working version of a Ring middleware that >>>> some of you might find useful. It's designed for web apps where, if you're >>>> overloaded, it's better to serve some requests quickly and fail the others >>>> than to try and serve all the requests and do it slowly. (My background is >>>> in telecoms, where that's often the best approach.) >>>> >>>> Specifically, you specify a target latency that you want 90% of >>>> requests to try and meet, and it applies the algorithm from >>>> http://www.eecs.harvard.edu/%7Emdw/papers/control-usits03.pdf to try >>>> and keep your latency below that threshold. The exact parameters of the >>>> algorithm are tunable, and different URLs or groups of URLs can have >>>> different targets and parameters. >>>> >>>> It still needs a bit of tidying - docstrings, cleaning up some of the >>>> Midje tests, and so on - but it works and I think the documentation is >>>> usable, so I'm announcing it now. >>>> >>>> Github (w/ docs): https://github.com/rkday/overload-middleware >>>> Clojars: https://clojars.org/overload-middleware >>>> >>>> Let me know if you have any feedback! >>>> Rob >>>> >>>> P.S. I threw together a simple demo (available from >>>> https://github.com/rkday/overload-middleware-demo) and tested it It >>>> works as designed - the URL wrapped in the overload middleware fails about >>>> 50% of requests, and so for the ones that succeed there's a noticeable >>>> speed improvement (80% of results are served in 120ms as opposed to 233ms >>>> for the unwrapped URL), though I suspect ab might be counting the immediate >>>> 503s in this result and throwing it off. If anyone has ideas for better >>>> tests, let me know! >>>> >>>> 2049 14:05:02 overload-demo $ for i in unwrapped wrapped; do ab -n >>>> 50000 -c 300 -q http://localhost:3000/$i; done >>>> ... >>>> Document Path: /unwrapped >>>> .. >>>> Failed requests: 0 >>>> ... >>>> Percentage of the requests served within a certain time (ms) >>>> 50% 178 >>>> 66% 204 >>>> 75% 216 >>>> 80% 233 >>>> 90% 358 >>>> 95% 1117 >>>> 98% 1211 >>>> 99% 3097 >>>> 100% 15196 (longest request) >>>> >>>> ... >>>> Document Path: /wrapped >>>> ... >>>> Failed requests: 25285 >>>> (Connect: 0, Receive: 0, Length: 25285, Exceptions: 0) >>>> Write errors: 0 >>>> Non-2xx responses: 25285 >>>> ... >>>> Percentage of the requests served within a certain time (ms) >>>> 50% 67 >>>> 66% 86 >>>> 75% 108 >>>> 80% 120 >>>> 90% 1028 >>>> 95% 1080 >>>> 98% 1287 >>>> 99% 3082 >>>> 100% 15120 (longest request) >>>> >>>> There's also no noticeable overhead in non-overload cases: >>>> >>>> 2050 14:07:30 overload-demo $ for i in unwrapped wrapped; do ab -n 50 >>>> -c 1 -q http://localhost:3000/$i; done >>>> ... >>>> Document Path: /unwrapped >>>> .. >>>> Failed requests: 0 >>>> ... >>>> Percentage of the requests served within a certain time (ms) >>>> 50% 33 >>>> 66% 33 >>>> 75% 33 >>>> 80% 33 >>>> 90% 33 >>>> 95% 34 >>>> 98% 35 >>>> 99% 35 >>>> 100% 35 (longest request) >>>> >>>> ... >>>> Document Path: /wrapped >>>> ... >>>> Failed requests: 0 >>>> ... >>>> Percentage of the requests served within a certain time (ms) >>>> 50% 33 >>>> 66% 34 >>>> 75% 34 >>>> 80% 34 >>>> 90% 34 >>>> 95% 34 >>>> 98% 34 >>>> 99% 34 >>>> 100% 34 (longest request) >>>> >>>> -- >>>> -- >>>> You received this message because you are subscribed to the Google >>>> Groups "Clojure" group. >>>> To post to this group, send email to clojure@googlegroups.com >>>> Note that posts from new members are moderated - please be patient with >>>> your first post. >>>> To unsubscribe from this group, send email to >>>> clojure+unsubscr...@googlegroups.com >>>> For more options, visit this group at >>>> http://groups.google.com/group/clojure?hl=en >>>> --- >>>> You received this message because you are subscribed to the Google >>>> Groups "Clojure" group. >>>> To unsubscribe from this group and stop receiving emails from it, send >>>> an email to clojure+unsubscr...@googlegroups.com. >>>> For more options, visit https://groups.google.com/groups/opt_out. >>>> >>> >>> -- >>> -- >>> You received this message because you are subscribed to the Google >>> Groups "Clojure" group. >>> To post to this group, send email to clojure@googlegroups.com >>> Note that posts from new members are moderated - please be patient with >>> your first post. >>> To unsubscribe from this group, send email to >>> clojure+unsubscr...@googlegroups.com >>> For more options, visit this group at >>> http://groups.google.com/group/clojure?hl=en >>> --- >>> You received this message because you are subscribed to the Google >>> Groups "Clojure" group. >>> To unsubscribe from this group and stop receiving emails from it, send >>> an email to clojure+unsubscr...@googlegroups.com. >>> For more options, visit https://groups.google.com/groups/opt_out. >>> >> >> -- >> -- >> You received this message because you are subscribed to the Google >> Groups "Clojure" group. >> To post to this group, send email to clojure@googlegroups.com >> Note that posts from new members are moderated - please be patient with >> your first post. >> To unsubscribe from this group, send email to >> clojure+unsubscr...@googlegroups.com >> For more options, visit this group at >> http://groups.google.com/group/clojure?hl=en >> --- >> You received this message because you are subscribed to the Google Groups >> "Clojure" group. >> To unsubscribe from this group and stop receiving emails from it, send an >> email to clojure+unsubscr...@googlegroups.com. >> For more options, visit https://groups.google.com/groups/opt_out. >> > > -- > -- > You received this message because you are subscribed to the Google > Groups "Clojure" group. > To post to this group, send email to clojure@googlegroups.com > Note that posts from new members are moderated - please be patient with > your first post. > To unsubscribe from this group, send email to > clojure+unsubscr...@googlegroups.com > For more options, visit this group at > http://groups.google.com/group/clojure?hl=en > --- > You received this message because you are subscribed to the Google Groups > "Clojure" group. > To unsubscribe from this group and stop receiving emails from it, send an > email to clojure+unsubscr...@googlegroups.com. > For more options, visit https://groups.google.com/groups/opt_out. > -- -- You received this message because you are subscribed to the Google Groups "Clojure" group. 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